Tufted carpet is widely used today in the United States and abroad. Such carpet is produced by tufting machines which are essentially multi-needled sewing machines. The tufting machines push or, more specifically, sew the face yarns of the carpet (also referred to as pile yarns) through a primary backing fabric, forming loops in the face yarns. The machines also hold the face yarns in place while the needles are withdrawn. The resulting loops formed by the face yarns are then either released to form loop-pile, tufted carpet, or cut to form cut-pile, tufted carpet.
A secondary backing fabric, attached to the backstitched side of the primary backing fabric, i.e., the side opposite the protruding face yarns, is used to hold the tufted face yarn in place and is typically attached to the primary backing fabric by a latex or other binding adhesive applied to the backstitched side of the primary backing fabric. It is well known, however, that the latex or binding adhesives, such as hot melt adhesives, employed by the carpet industry must be cured prior to use, and that the latex and binding adhesives may emit volatile organic chemicals and odors. Consequently, the reduction or elimination of the latex or binding adhesives is seen as being highly desirable.
In addition to improving the quality of the air inside buildings and other like places where carpet is used, the elimination of latex and adhesives provides for a much more easily recyclable carpet. That is, without the latex or adhesives, all of the components of the carpet, including edge trim, can be easily recycled. Thus, limited dump site space should no longer be a problem for the carpet industry. Moreover, the carpet is capable of using only one fiber material, such as polypropylene, or nylons, for the face yarns and primary and secondary backing fabrics, thereby eliminating the necessity that the individual compositional components be separated prior to recycling.
Attempts have been made heretofore to produce non-adhesive bonded carpet. In fact, Hoechst Celanese has recently developed a new method of constructing carpet using 100 percent polyester face yarns and backing fabrics. That carpet system eliminates all other fibrous materials, including polypropylene and nylon, as well as latex or binding adhesives.
The carpet produced by Hoechst Celanese uses undyed polyester spun yarns as the face yarns of the carpet. These face yarns are tufted or pushed through a primary backing fabric made from polyester nonwoven fibers. A secondary backing fabric also made of nonwoven polyester fibers is sewn to the back of the tufted primary backing fabric to lock the tufted face yarns in place, to cover the back of the primary backing fabric, and to add strength and dimensional stability to the carpet beyond that which is provided by the primary backing fabric itself.
Uniquely, at least one of the backing fabrics (either the primary or the secondary) of the Hoechst Celanese carpet contains low melt polyester fibers having a lower melt point (melt point equals approximately 105.degree. to 110.degree. C.) than the polyester fibers found in the other backing fabric. Consequently, when the secondary carpet backing fabric is heated during or after dyeing, wet processing, and/or drying, the polyester fibers of the secondary and primary backing fabrics melt together, thereby remaining attached to each other and keeping the tufted face yarns from being removed easily.
While this process is suitable for use with polyesters and low-melt polyesters, fabrics employing the same material having the same melt temperatures are not suitable for the Hoechst process. Moreover, unlike polypropylene, polyester as used by the carpet industry is generally not predyed during the fiber-forming stage of production. Instead, polyester is dyed through the use of "wet processing" with conventional dyeing equipment. Generally, the standard types of dyeing equipment used in the carpet industry are beck and Kuster (or continuous dyeing). Beck is used for dyeing fabric in rope form and consists essentially of a tank and a reel to advance the fabric. Kuster essentially wets the carpet or fabric, applies dyes and any other necessary chemicals with a doctor blade, fixes the dyes in a festoon steamer, and washes and dries the carpet or fabric in a pass through the equipment. It is a requirement of the Hoechst process that the carpet be dried thoroughly to remove all liquid. Preferably, such a step is accomplished using a flow-through dryer which blows air from both above and below the carpet. This drying process activates the low melt polyester fiber and binds the system together.
Thus, with both of these types of dyeing equipment, the carpet is wetted, dyed and dried. Drying after dyeing thus activates the low melt fiber components found in one of the two backing fabrics to bind the two backing fabrics together. Nevertheless, tufted carpet has not been made heretofore in the absence of wet processing, which carpet is devoid of latex and adhesives.